A variational constitutive model for porous metal plasticity
This paper presents a variational formulation of viscoplastic constitutive updates for porous elastoplastic materials. The material model combines von Mises plasticity with volumetric plastic expansion as induced, e.g., by the growth of voids and defects in metals. The finite deformation theory is based on the multiplicative decomposition of the deformation gradient and an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small strains to finite deformations. Thus the time-discretized version of the porous-viscoplastic constitutive updates is described in a fully variational manner. The range of behavior predicted by the model and the performance of the variational update are demonstrated by its application to the forced expansion and fragmentation of U-6%Nb rings.
© Springer-Verlag Berlin Heidelberg 2005. Received: 29 July 2004 / Accepted: 14 March 2005 / Published online: 6 July 2005 We are grateful for the financial support provided by the US Department of Energy through Caltech's ASC Center for the Simulation of the Dynamic Response of Materials.